1. Field of the Invention
The present invention relates to drive control circuits for the on-off control of the hydraulic drive for elevating and lowering the seat of a dental treatment table, as well as the forward and backward tilting of a backrest of the dental treatment table by means of a pneumatic type pressure control valve.
2. Prior Art
As is known in the prior art, the vertical movement of a seat and the forward and backward tilting of the backrest can be provided by supplying or withdrawing oil pressure through a hydraulic drive circuit to and from hydraulic cylinders. However, in a conventional type, many electrical parts are utilized. For example, a relay switch is used in the hydraulic pump operation circuit and a solenoid is used in the hydraulic drive circuit. Furthermore, such circuits operate on a low voltage which is stepped down by a transformer. Consequently, in view of the power consumption, burning out of the transformer by continuous use, etc., there has been a long felt need for finding a substitute for electric controllers.